then it is not a matter of influence but of direct alteration. You would not want your child to be given an actual third eye, and represented as an anamoly in a circus, and remembered thus for the rest of his days by the majority of the population, with only your kith and kin recalling that he or she was once a two eyed child living a typical life.

Also there are changes, and then there are *cue Bowie music* CH CH CH CH CHANGEEES!

The former is managable, can work well, and is to be expected. . . the later

There are omissions and additions that really don't greatly alter the work, especially those additions that could easily have occured, for example, there being a female Elf guard named Tauriel present in Thranduil's halls, or Gandalf briefly visiting The Olde Forest to ask if Old Bombadil has noted any dark and unusual happenings in his part of the North of Eriador. . .

Then there are CHANGES that upset the entire order of the story and challange the relative facts of the source. . . i.e. The Black Arrow fails to take down Smaug, and Tauriel shows up and puts fifty more arrows into the same vulnerable spot in the space of thirty seconds, or Tom Bombadil puts Gandalf under a pleasant and enchanted slumber, and tells him to rest from his labours whilst Old Tom sees to his errands, reminds Saruman of whom he was truly sent in service of, and helps to flush out that schemeing Sauron.

In essence, its all the difference between, "well that could have happened, but its not in the story etc." and "oh HELL naaaw! That did not, could not and WOULD not have happened! Where the devil are you getting these crazy notions?!" lol "Hear me, hounds of Sauron, Gandalf is here! Fly if you value your foul skins, I will shrivel you from tail to snout if you step within this circle!"

"Do not be to eager to deal out death in judgement. Even the very wise cannot see all ends."